Thomas a



(No Model.)

T. A. EDISON.

ELEGTRIG LIGHTING SYSTEM.

P19439392. Patented Oct. 28, 1890.

UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY, ASSIGNOR TO THE EDISONELECTRIC LIGHT COMPANY, OF NEW YORK, N. Y.

ELECTRIC-LIGHTING SYSTEM.

SPECIFICATION forming part of Letters Patent No. 439,392, dated October28, 1890.

Application filed August 22, 1882. Serial No. 69,995. (No model.)Patented in England March 3, 1882, No. 1,023.

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of Menlo Park, in the county ofMiddlesex and State of New Jersey, have invented a new and usefulImprovement in Electric-Lighting Systems, (Case No. 473,) of which thefollowing is a specification.

Said invention is patented in Great Britain by Letters Patent No. 1,023,dated March 3, 1882.

The object I have in View is to produce means to be used in connectionwith dynamo or magneto-electric machines supplying electric lamps orother translating devices arranged in multiple are, which means willprevent injury to the machine or machines when an abnormally largecurrent is caused to flow by the addition of more lamps or othertranslating device than the plant has capacity to furnish, and will atthe same time notify the engineer of the condition of affairs. Thisobject I accomplish in the following manner: A piece of safetycatch wireor material is placed in one of the conductors of the main orconsumption circuit. This safety-catch is of such size and characterthat when more lamps are put in circuit than the plant is designed tofurnish, and before the machine or machines are injured by theabnormally-large flow of curren it will burn out and break the circuitbetween the generator and the transflating devices. In a shunt aroundthis safetycatch are arranged a vibrating bell and a resistance, theresistance being suificient to prevent the striking of the bell when thesafety-catch is intact; but when the safetycatch is burned out thecurrent passes through the bell-circuit and operates the bell-hammer.The lights at the same time Will drop to a red heat. The engineer thenremoves a sufficient number of lamps and replaces the safety-catch. Theforegoing will be better understood by reference to the drawing, inwhich the figure is a diagrammatic view of the parts.

A represents adynamo or magneto-electric machine; 1 2, the main orconsumption circuit, and a a incandescing electric lamps or othertranslating devices located in multipleare or derived circuits.

The field-circuit of the machine may be a multiple-arc circuit 3 4 from1 2, and be provided with an adjustable resistance R.

B is a piece of safety-catch wire or material placed in 1 or 2 betweenthe lamps and the machine A. In a shunt 5 or 6, around B, are arranged aresistance R and a vibrating bell composed of electro-magnet h, spring'5, bell-hammer 7c, and gong l.

WVhat I claim is- 1. The combination of one or more electricalgenerators and translating devices supplied therefrom, of a safety-catchfor preventing injury to said generator or generators when theircapacity is exceeded and an alarm adapted to give notice of thedestruction of said safety-catch, substantially as set forth.

2. The combination, with the safety-catch between the translatingdevices and the generator, of an alarm arranged in a shunt-circuitaround said safety-catch, substantially as and for the purpose setforth.

This specification signed and witnessed this 12th day of August, 1882.

THOMAS A. EDISON.

Witnesses:

H. W. SEELY, E. H. PYATT.

